How Are Speed Limits Enforced by Aircraft?

When you’re traveling for the holidays later this month, you might notice some signs on the highway that read “speed limit enforced by aircraft.” If you’re like me, those signs conjure images of the cops scrambling a team of jet fighters to take a driver with a lead foot off the road. In reality, it’s a little less exciting. Here’s how it works in Pennsylvania (where I live and always obey the speed limit), according to the state police.

Certain lengths of highway that are known to be trouble spots for speeding are targeted by the State Police Aerial Reconnaissance Enforcement (SPARE) (other states will have their own names for similar programs) and marked with start and finish lines at a set distance from each other. Two officers—a pilot and a spotter—cruise over these stretches in a small fixed-wing aircraft.

When a vehicle crosses the start line, the spotter uses a specially-designed stopwatch (some police departments also use VASCAR systems) to clock the car’s speed through the enforcement zone. If they determine that a vehicle is speeding, the officers in the plane radio another officer on the ground, who pulls the vehicle over and issues a ticket.